Lesson 2: Commas with Sentence Interrupters and Introductory Elements

Definition

Use commas to set off an expression that interrupts a sentence.

Explanation

Think of sentence interrupters as little asides or side comments within a sentence. They add extra information but aren't part of the main action. To show that this information is an interruption, you must use commas to separate it from the rest of the sentence, creating a natural pause.

Examples

• Michael, did you see that bird fly by? [The word Michael interrupts the rest of the sentence, so it is followed by a comma.]
• The dog, who loves to chase squirrels, ran across the yard. [The added information who loves to chase squirrels interrupts the sentence and is set off by commas.]
• We will finish the project on time, of course. [The added information of course interrupts the sentence and is preceded by a comma.]

Definition

Use commas to set off an expression that interrupts a sentence.

Explanation

When an interrupter is nonessential, it means the information is extra and the sentence would make sense without it—so you must use commas. If the information is essential to understanding who or what the sentence is about, it is a vital detail and you should not use commas.

Examples

• Nonessential: My uncle, who is a firefighter, visited my school. [The clause who is a firefighter is bonus information and is set off by commas.]
• Essential: The student who raised her hand may ask a question. [The clause who raised her hand is essential to identify which student; no commas are used.]
• Nonessential: The final book in the series, my favorite one, was very exciting. [The phrase my favorite one is a nonessential appositive that adds extra detail.]

Definition

Use a comma after certain introductory elements.

Explanation

An introductory element is a word, phrase, or clause that appears at the very beginning of a sentence, before the main subject. It acts as a warm-up for the main idea. You must place a comma after these introductions to signal that the main part of the sentence is about to begin.

Examples

• Well, I suppose we could go to the park instead. [The introductory word Well is followed by a comma.]
• At the back of the closet, I found my old photo albums. [The introductory phrase At the back of the closet is followed by a comma.]
• When the timer buzzed, Maria took the cake out of the oven. [The introductory clause When the timer buzzed is followed by a comma.]